The controversy of C. Schmitt and H. Kelsen on the guardian of the constitution held in the 1930s clearly demonstrates the relationship between the postulated basis of the validity of law, the definition of the essence and limits of justice and the model of the guarantee of constitution. С. Schmitt identifies three grounds of the validity of law: norm (normativism), decision (decisionism), order (institutionalism). Based on the assumption of law as a specific order, the author proposes his own model of constitutional guarantee - the guardian of the constitution “in an institutional sense”, which is the head of state who preserves order by extraordinary and potentially unlimited powers. In his opinion, president is such a guardian in the concrete constitutional order of the Weimar Republic. The court is interpreted by a German lawyer as an institution of a particular order. C. Schmitt’s concrete-order thinking defines the boundaries of justice - it is “political”, which is understood as an extraordinary degree of intensity division into public “friends” and “enemies”. Going beyond these boundaries the court finds itself in the sphere of political struggle, where independence, neutrality and objectivity, and, consequently, justice are impossible. These ideas on the essence and limits of justice constitute the theoretical basis on which C. Schmitt builds criticism of the H. Kelsen’s judicial model of the guarantee of constitution. H. Kelsen reduces the legal order to a hierarchical system of norms, the validity of which arises from the so-called “basic norm”. The thesis on the identity of lawmaking and law enforcement follows from the normative point of view of H. Kelsen which, combined with the independence of the judiciary, constitutes the theoretical base of the judicial model of guaranty of constitution. Criticizing the views of H. Kelsen, C. Schmitt argues that a constitutional judge, by resolving doubts regarding the substance of the constitutional norm, creates its substance independently, i.e. makes a political decision, and, consequently, acts as a constitutional legislator. The politicization of justice is a particular case of escalation of the “political”, from which the guardian “in an institutional sense” is intended to protect the order. Consequently, the constitutional judge reveals himself as a new sovereign at which point a threat of a sovereign’s duplication and a collapse of political unity emerges. Thus, the origin of disagreement between two significant lawyers does not lie in the field of pragmatic reasoning on the feasibility and effectiveness of constitutional guarantee models, but it occurs because of different interpretation of the basis of validity of legal order, which predetermines their diametrically opposed approaches on defining the essence of justice and its boundaries.